Can I still upgrade my phone to a newer phone that Verizon no longer carries? (Prepaid)?

I have a prepaid Samsung Smooth, but I want to upgrade to the prepaid Verizon Blitz. Verizon doesn't carry the Blitz anymore, but I bought it from an outside source. I want to know that even if they don't carry the phone if I could still switch it from my Smooth to the Blitz.